Method of distilling tar



Jan. 2, 1934. s'. .P. MILLER 1,942,371

METHOD OF DISTILLING TAR Filed March 23, 1928 3 Sheets-Sheet l INVENTOfiMW ATTORNEYS Jan. 2, 1934.

s. P. MILLER 1,942,371

METHOD OF DISTILLING TAR Filed March 23, 1928 3 Sheets- Sheet 2 )(Jer s[ana e? ATTORNEYS Jan. 2, 1934. s. P. MILLER 7 METHOD OF DISTILLING TAR3 Sheets-Sheet 3 Filed March 23, 1928 ATTORNEYS Patented J an. 2, 1934UNITED STATES PATENT OFFICE METHOD OF DISTILLING TAR Stuart ParmeleeMiller, Englewood, N. J., as-

signor to The Barrett Company, New York, N. Y., a corporation of NewJersey Application March 23, 1928. Serial No. 263,990

8 Claims.

This invention relates to improvements in the distillation of tar,tarryoils and pitch and in-,,

In the ordinary operation of by-product coke l ovens, the gases producedby the coking operation pass from the individual ovens thru uptake pipesand goose-necks to a collector main common to the ovens of the battery.The gases, commonly known as foul gases, leave the ovens at hightemperatures, for example, at 600 to 700 C., or higher, and carry aconsiderable proportion of pitchy material, tars and oils as well assolid particles of coke, dust, etc. Ordinarily, the gases are cooled bythe application of sprays of ammonia liquor or ammonialiquor and tar inthe collector main, or by circulating ammonia liquor and tar thru themain, the heat in the gases being thereby dissipated and lost. The rapidcooling causes separation of tar containing heavier oils in thecollector main. Further cooling is efiected in the cross-over main whichconnects the collector main to the condensing system and additional tarmay be separately recovered from this part of the system. In the coolersor condensers light tars or tarry oils are separated.

The tars and tarry oils are blended and are ordinarily shipped from thecoke oven or other coal distillation plant to a tar distillation plantfor distillation and separation of the oils, and the production ofpitches of varying quality. Handling costs, freight charges anddistillation costs,

including fuel. capital and maintenance expense for the specialequipment required for distillation, add to the cost of the tardistillation prod ucts.

According to the present invention, high tem perature coal carbonizationgases are admitted under the surface of a body of pitch, tar or oil andby bubbling up thru it the hot gases not only eifect distillation butalso agitate the body of material causing a continual change of thesurface exposed to the hot gases.

The material which is to be distilled according to the presentinvention, may be coal tar produced at coke oven plants or gas house tarproduced at gas retort plants (vertical, horizontal, or inclined), watergas tar, or tar or tarry oil from another source or pitch resulting fromthe partial distillation of tar. Such tars frequently contain aconsiderable percentage of water intimately admixed or combinedtherewith,

particularly where Water or ammonia liquor is employed for separatingand condensing the tar constituents from the coal distillation or othergases, and such tars may, if desired, be dehydrated before beingdistilled according to this invention, or may be dehydrated as part ofthe process.

The hot coal distillation gases leaving coke ovens, gas retorts, etc.,carry with them solid impurities, such as free carbon, coal dust, etc.The gases also contain in suspension very finely divided particles oftar known as tar fog. On

bringing this gas into contact with liquid in the still, such entrainedsolids and liquids are removed to a greater or less extent. When thegases are bubbled up thru the liquid as fine bubbles, the surface ofcontact is large and the scrubbing action of the liquid on the gases isgreater than when the gases are admitted to the still as larger bubbles.The depth of liquid thru which the gases pass is another factoraffecting the thoroughness of the scrubbing.

The gases which are passed thru the body of I tar or oil, to effect thedistillation of the tar or oil, keeping it in motion continuouslypresenting new' surfaces from which vapors arise, are the hot gasesproduced by a coal carbonization or gasification operation. The hotgases may be hot coke oven gases or hot retort gases or hot water gas,etc. In the case of hot coke oven gases, for example, the gases escapefrom the coke ovens at a temperature, for example, from GOO-700 C., oreven higher in some cases, and tfese gases, after minimum, or at leastregulated cooling'in the collector main, may be used for distillation bypassing them under the surface of the tar or oil to be distilled andallowing them to bubble up thru the body of liquid. The high temperaturegases withdrawn from, gas retorts, water gas retorts, producers,-etc.,may be used in a similar way to efiect distillation.

The mains connecting the coke ovens, retorts, or other coalcarbonization apparatus as well as the stillitself, may advantageouslybe insulated. The still is preferably placed adjacent to or even uponthe top of the carbonization apparatus to minimize the amount of heatlost by radiation. According to the present invention, the hot gases mayadvantageously be passed up thru a considerable depth of the liquid tobe distilled. The liquid may in addition be mechanically agitatedifdesired. The efliciency of the operation is improved by securingprolonged contact of the gases. with the liquid by introducing the gasin sub-divided form and by passing the subdivided gases up thru aconsiderable depth the liquid. In operating in this manner, the g sesare kept in contact with the liquid for a prolonged period of time andmore efiective agitation of .the body of the liquid is secured. Thepressure'required to force the gases thru the body oftar or oilincreases with increase in the depth of liquid thru which the gases mustpass. In actual operation the proper relation between the variousfactorsmust be adjusted in such a way as to give the desired efficiencyof operation under the particular conditions presented.

The depth of tar or oil in the still may be varied. If the gases areadmitted into the still near the bottom so that the depth of liquid inthe'still is only slightly greater than the depth of liquid thru whichthe gases pass, the liquor in the still will be thoroughly agitated.Although this is the preferred method of operation, it is possible, onthe other hand, to provide a body of I tar or oil for distillation whichmay be of a much greater depth in the still than the depth of tar or oilthru which the gases pass. r The gases may be conducted into the body ofliquor to be distilled thru small openings in a pipe or otherdistributing means submergedin the contents of the still, or the gasesmay be admitted into the still, thru openings in the bottom of the stillitself. Preferably, the gas is admitted to the still'thru a multiplicityof small perforations in suitable distributing means in order that thegas may be divided into many small streams which will bubble up thru thecontents of the still thereby producing greater surface contact betweenthe gas and the contents of the still than if a fewer number of streamsof gas were provided. Any suitable means for causing the gas to bubbleup thru the body of liquor to be distilled may be utilized. Pressure maybe applied to the gases and vapors in the a still, or a reduction inpressure may be main- .tained above the body of tar or oilin the still.

The still may be of any suitable shape. In the drawings the still isshown as a cylindrical tank. The still is preferably insulated. Pressuremay be applied by means of an ordinary exhauster placed between the ovenor retort, etc., and the still, or an exhauster or pump may be situatedbeyond the still to create a vacuum suiiicient to draw the gases thruthe still.

This invention is well adapted for continuous operation. When operatingon this basis, tar or oil issupplied and unvolatilized, residue iswithdrawn continuously or at frequent intervals am the rate of additionto and withdrawal from the still is at all times regulated soas tomaintain controlling the time of contact between the liquor and thegases and regulating the quantity of each, and properly controllingother factors, such as the temperature of the liquid and gases ad;

mitted to each-still, etc., the distillation efiected may be controlled.

Where more than one still is employed the gases leaving several stillsmay be combined and passed thru a singlecondensing unit or the gasesfrom each still may be treated separately to recover distinct productswhich may be of rare-determined boiling range. The non-volatilizedresidue from reaaev "vidual stills, which, by proper manipulation, may

have a predetermined boiling range or other desired property orproperties.

' For example, when several stills areemployedand oil, for example ispassed thru the stills in series, and subjected to fresh hot gases, thegases leaving each still may be passed thru a separate condensing systemso that a low boiling oil will be condensed from the vapors carried bythe gases leavingthe first still in the series and higher boilingfractions condensed from the other stills.

By drawing off a portion of the residue from the first still into aseparate container and passing the balance into the second still of theseries, a residual oil of wide boiling range with a predetermined lowerlimit may be recovered. Residues of less wide boiling range may be drawnfrom the succeeding stills.

Various arrangements of stills, hot gas mains and recovery systemspermit a variety of operations to be carried out utilizing the "generamethod of this invention.

Although the invention is of broader application, it will be describedparticularly in connection with coke oven operation. The gas employedforthe distillation may be withdrawn at practically its maximum temperatureas it comes from the coke ovens, or the gas may be employed at asomewhat lower temperature.

Where the gas is not'to be used at or near its maximum temperature, thetemperature of the gas may be regulated by the treatment to which itissubjected prior to its use in the distillation operation. The gas maybe sprayed with ammonia liquor in the goose-neck and in the collectormain, or it may be sprayed with tar or oil in the goose-neck or in thecollector main, or it may be sprayed with a mixture of the two, or inboth the goose-neck and collector main, and the gas thus cooled. to aregulated lower temperature before use for distillation.

Due to the greater specific heat and heat of vaporization otwater,spraying with water or ammonia liquor produces a greater cooling efiecton the gases than spraying with an equal amount of tar or oil. Byregulating the quantity of the water or tar, etc., sprayed in the gasesprior to their passage up thru the body of tar or oil to be distilled,the temperature of the gases used for the distillation canbe'controlled. The temperature of the gases may likewise be controlledby' I regulating the temperature of the spray. By limiting the amount ofcooling, the gases can be employed at a regulated high temperature, suchthat they have a rapid distilling action in the still.

The temperature and amount of the gases used may be regulated accordingto the distillation which is to be carried out. If light tarry oils orlight tars only are to be distilled, the temperature of the gases usedin the distillation need not be as high or the amount of the gasesemployed need not be as great, as when higher boiling oils are to bedistilled from .tar or from pitch.

Where maximum' distillation is desired, the,

top of the coke oven block in close proximity to ,given ofi in thisoven,

the uptake pipe, the gases can be employed at a temperatureapproximating that at which they leave the uptake pipes. By using suchhigh temperature gases, rapid heating and distillation can be effected,and pitches of high melting point produced, as well as high yields ofoils, including high boiling oils.

In the operation of a coke oven the gases produced are not of uniformcomposition. At the start of the coal distillation process, oils, etc.,are liberated from the coal in large quantities and the first gasesgiven ofi are rich in volatile products. The gases given off during thelatter part of the coal distillation, for example, during the lastthirty percent of the operating time under normal conditions, contain aless percentage of condensable constituents than the richer gases givenoff during the first part of the distillation, and are known as leangases. Y

There is in many cases an advantage in using either the rich gases orlean gases separately in distillation of tar, according to the presentinvention. For example, lean gases are capable of taking up a greaterquantity of oil and other vapors per unit volume of tar or oil thruwhich they pass than an equivalent amount of a rich gas which alreadycontains more volatile constituents than does the lean gas, the gastemperature in each case being the same. Rich gases contain a largeramount of condensable vapors which admix with the distilled vapors andare condensed therewith.

The tars entrained in rich gases are lower in free carbon content thanare the tars entrained in lean gases. Therefore the free carbon contentof the residue in the still may be regulated or controlled by the use ofrich or lean gases since more or less of the tar entrained in the gasesused for distillation will be removed from the gases and be retained inthe residue in the still.

In order to take advantage of either rich or lean gas, the coke oven maybe equipped with two collector mains, each of which is adapted to bethrown into communication with the uptake pipe from each of the ovens inthe battery to which the collector mains are connected thru a system ofvalves. As an example, during the first of the distillation operationin-any one oven, this oven will be thrown into communication with thecollector main which is connected directly with recoveryapparatus. Afterthe distillation has progressed to the point where lean gases are beingit will be thrown into comntunication with the other collector mainwhich is in communication with the still.

By the usual rotation of the ovens in a battery of average size, therewill at all times be a fairly continuous and uniform production of leangases. so that the quantity and temperature of the gases passing thruthe still will be fairly un form at all times. Rich gases may, in manycases, be

/ desired for distillation, and can be utilized by my invention.

Depending upon the extent to which the distillation of the tar or tarryoil is carried, substantially only the lighter oils may be removed fromthe body of tar or oil, leaving a tar or very light pitch in the still.By carrying the distillation further, heavier constituents will bevolatilized and recovered from the gases, and a heavier tar or pitchwill remain as a residue in the still.

The distillation can be accomplished in numerous ways. For example, alarge volume of relatively low temperature gases may be used, or asmaller volume of relatively high temperature gases, as they come fromthe ovens, may be used. The tar may also be preheated before beingbrought into contact with the gases.

The gases escaping from the distilling operation will carry in vaporformthe constituents volatilized from the tar and will contain in additionthereto such of the vapor constituents carried by the gases entering thestill as have not been removed by contact with the tar or oil beingdistilled. In the case of hot coke oven gases employed for thedistillation of coal tar produced by the coke ovens, the hot gases afterthe distillation operation will contain uncondensed constituents fromthe coal distillation as well as added vapor constituents driven offfrom the coal tar during the distillation.

Higher boiling constituents carried by the hot gases from the ovens maybe condensed in the still and the latent heat of condensation absorbedin the distillation operation, in which case condensate from the gaseswill be blended with the non-volatilized residue of the tar or oil addedto the still and drawn off from the still as such. By using coal tarproduced at the coke oven plant while it is still hot before it has hadopportunity to cool, a saving in heat may be effected.

- The gases from the still can be treated for the condensation andrecovery of the desirable constituents contained therein as well as forthe recovery of ammonia carried thereby. Where only a portion of thegases from the coal distillation apparatus are passed up thru tar or oilin the still, those gases which are enriched by passing thru the tar oroil can be treated in a separate recovery system and the oils condensedtherefrom will be a mixture of the oil constituents normally in thegases and those added to the gases during the distillation, whereas thecondensate from the remainder of the system will contain only the coaldistillation products normal to the gases. The enriched gases can alsobe treated in the same recovery system with the remainder of the gasesproduced by the coal distillation.

In a coke oven plant where several batteries of coke ovens are operated,the rich or lean or normal gases from one battery may be employed fordistilling tar from the other batteries, or a part of the gases from onebattery may be so employed. The gases used in the distillation may beonly a portion of the gases collected in the collector main and may betaken ofi one end of the collector main, or all the gases passing thruthe collector main may be utilized e. g. by taking them off thecenter-box according to the customary practice. A tar or oil, other thana coaltar product, can be distilled and the condensable constituentsrecovered in a separate recover system without contaminating the balanceof the coal-tar products produced.

Where the distillation is carried out as a batch operation, the tar oroil is progressively heated by the hot gases and the lighterconstituents are progressively removed therefrom until the distillationhas been carried to the desired point. after which the operation can bediscontinued, and the residue withdrawn, and the still recharged withfurther tar or oil to be distilled.

Due to enrichment of the gases in clean oil vapors volatilized from thematerial in the still,

the oils removed in the condensers following the still will contain lessfree carbon and pitch impurities than would oils condensed directly fromgases not used for distillation.

In some cases it may be desired to regulate the character of the residueof distillation as respects erage boiling point increase.

free carbon content or as respects the type of oil remaining in or addedto it. This may to a greater or less extent be accomplished by usingrich or lean or intermediate gases for distillation. Rich gases containtar with a relatively low free carbon content and they contain also oilsof lower average boiling point and lower specific gravity than do leangases. Rich gases contain a greater amount of tar than lean gases. Asthe gases get leaner the amount of tar contained in them decreases, thepercentage of free carbon in the tar increases, the amount of oilcontained in them decreases and its specific gravity and av- Since inthe distilling operation more or less of the tar contained in the gaseswill be retained in the residue and more or less of the contained heavyoils Will be condensed and retained in the residue, the character of theresidue may to some extent be controlled by choosing the proper gasesfor distilla-' 'tion. Such gases may be rich, lean or intermediategases.

The invention will be further described in connection with theaccompanying drawings illustrating apparatus embodying the invention andadapted for the practice of the process of the invention, but it isintended and will be understood that the invention is illustratedthereby but is not limited thereto.

apparatus in which two collector mains are shown with provision for useof rich or lean gases for distillation.

Fig. 3 is an enlarged detail showing in crosssection the relation of twocollector mains of.

Fig. 2 to each other and the coke oven;

Figs. 4, 5 and 6-give details of the still shown inFig. 1.

. In the drawings, 5 indicates a coke oven battery with the usual uptakepipes 6, collector main '7, sprays 8, center-box 9 and cross-over main10. Wet condensers 11 and 12 are provided for condensing tarry oilvapors passing with the gases thru the cross-over main. From thecondensers the gases pass thru the pipe 13 and exhauster 14 to the exitpipe 15, from which they may be passed to ammonia, saturators 'or benzolrecovery apparatus or other suitable apparatus.

Condensate from the condensers 11 and 12 is drawn on into the decanter16 from which and-- monia liquor is withdrawn into the tank 17 and, farinto the receiver 18. Tar and ammonia liquor from the collector main,collecting in the centerbox 9, are drawn thru pipe 20 into the decanterfrom which ammonia liquor. is withdrawn into the receiver 21, and tarinto the tank 22, or the tar and ammonia liquor may be allowed to runthru the cross-over main 10 and be, drawn off at 10 to a decanter notshown.

The collector main and goose-necks may be sprayed with tarirom 18 thruthe pipe 23 .or with tar from 22 thru the pipe 24, or with ammoniaand/or tar from another source thru pipe 25.

One end of the main may be sprayed with tar and one with ammonia liquorby the use of line 24 and valve 33. The collector main may be flushedwith tar and/or with ammonia liquor thru lines 5' and 8'.

By shutting ofi the sprays 8 and by flushing themain the gases may beheld at high temperature and accumulation of achd lard pitch in the mainmay be prevented.

The still 26 may be supplied with tarfrom 22 thru the pipe 27, or tarryoils from the-tank 18 thru the pipe 28, or tar or oils from. an outsidesource thru/ the pipe 29. If necessary, pumps may be provided, asindicated by the reference numerals 30. The feed pipe to the still isequipped with a heat interchanger 31.

Gases from the collector main are led to the distillation in the still.The entire system or any of its parts may be adequately insulated. Thegases leaving the collector main pass thru the pipe 32 and are caused tobubble thru perforations 34 in the pipe 35 in the bottom of the still.

gases may be conducted into the contents of the still thruany suitabledistributing means submerged in the liquor in the stilL' Although in theaccompanying drawings a single pipe 35 is shown, any number of suitablemeans may be provided. By making the outlets for the gas small, thesurface contact between the gas and the contents of the still is madelarge and the emciency of the operation may be increased.

The hot gases, on being brought into contact with the contents of thestill, carry off with them the desired volatile constituents of thecontents of the still. These mixed gases and vapors pass ofi from thestill thru the pipe 36 thru which they may be passed to any suitablecondensing means such as the condensers 37 and 38, in which case theywill be led thru pipe 39 to the pipe 15, or they may be lay-passed thruthe pipe 40 and con- .veyed to the condensers 11 and 12 or othersuitable condensing means thru the pipe 41.

Condensate from the condensers 3'7 and 38 is collected in thedecanter42. Two separate oil ,fractions may be collected bydrawing oi? thecondensate from one condensingsection thru line 28' to a decanter notshown and'drawing ofi the other to decanter 42. Oil from 42' may besupplied to the collector main or still as shown. Bafile means (notshown) may be provided at the gas outlet from the still toprevent-liquor entrained in the gases from passing over to thecondensers.

The still may be operated as a batchoperation This still may be of anysuitable shape and the trolling the extent of the distillation a heavytar or light pitch may be produced in the still.

In the apparatus shown in Fig. 2, the parts of r the equipment have beenmade to correspond as far as possible with the corresponding parts ofFig. 1"as indicated by the numerals; 305 represents the coke ovenbattery th' two collector mains 307 and 307. The cross-over main 310leads to condensers 311 and 312. 1 From 156 the collector main 307', thegases are conducted thru the main 332 into the still 326 and from thenceby the pipe 336 to the conductors 337 and 338 or thru the by-pass 340.Residue from the still is drawn off thru the pipe 344 into the storagereceptacle 345. Tarry oils are drawn off the condensers 311 and 312 intothe decanter 316, from which ammonia liquor is drawn off into thereceiver 317 and tarry oil into 318. From 318 the tarry oil may bepumped by pump 331 thru the heat interchanger 331' into the still.

Instead of supplying the still with tarry oil from this source, tar oroil from any outside source may be supplied thru the pipe 370, or tarfrom either of the collector mains may be drawn off thru thecenter-boxes 309 and 309 and the pipes 3'71 and 372 to the decanters3'73 and 3'74 from which ammonia liquor is drawn off into the storagetank 375, and the tar which is collected in the two receivers 3'76 and377 may be supplied to the still thru the pipes 378 and 379, re-

spectively.

When it is desired to spray tar without ammonia liquor into the gasesgoing to the still the tar may be supplied thru the lines 380 and thesprays connected thereto. The collector main may be flushed with tarand/or ammonia liquor thru lines 305 and 376'. By shutting off thesprays the gases may be held at high temperatures, and

by flushing the main accumulation of solid hard pitch may be prevented.

The character and quantity of the residue withdrawn from the still andof the clean oils condensed from the enriched gases leaving the still isdependent upon many factors, such as the quantity and temperature of thegases, which depend to some extent upon the spraying of the gases in thecollector main and also 'upon the character and quantity of tar or oilsupplied to the still. Controllable variables permit regulation of theprocess to produce the desired tars or pitches from the still and oilsof the desired quality from the condensers.

I claim:

1. The method of distilling heavy hydrocarbon material in liquid form bythe heat of hot coal distillation gases resulting from the distillationof coal, which comprises separately collecting the gases from acontrolled period of the coal distillation operation, bubbling them at atempera comprises causing hot coal distillation gases from the coaldistillation-apparatus of'the plant at a temperature above the dewpointof oil vapors therein to bubble up thru a body of the hydrocarbonmaterial, whereby constituents thereof are volatilized by the heat ofthe gases and pitch residue is produced, continuously adding freshcooling them to tillation gases.

3. The method of distilling heavy hydrocarbon material in liquid form,which comprises causing fresh hot coal carbonization gases to bubblethru the hydrocarbon material so as to heat the material and effectsubstantial cooling of the gases, agitate it and effect the removal ofvolatile matter therefrom; and cooling the resulting gases to condensedistillate oils therefrom.

4. The method of distiling comprises causing fresh hot tar-laden cokeoven gases to bubble up.thru a substantial depth of a body of tar whiledistilling it, thereby imparting heat to the tar, facilitating theremoval of oil vapors from the tar, removing entrained tar particlesfrom the gases and incorporating them in the pitch residue formed, andcooling the resulting gases to condense distillate oils therefrom.

5. The method of operating a coke oven battery comprising a plurality ofovens in which coal is being distilled, which comprises withdrawing andmixing hot fresh coal distillation gases from from the distillation tocontar to pitch, which a plurality of the ovens, causing the hot mixedirlwhich coal is being distilled, which comprises Y collecting thehotcoal distillation gases from a portion of the ovens or retorts of theplant and separate tar, collecting at least a portion of the tar as abody thereof, collecting hot coal distillation gases from other ovens ofthe plant and bubbling'them while still at a high temperature up througha substantial depth of said body of tar so as to distill the tar by theheat of said gases. r

' '7. The method of distilling heavy hydrocarbon material in liquid formand containing volatile constituents, which'comprises causing fresh hotcoal carbonization gases while still at a temperture above about 300 C.after their production to'bubble through a substantial depth of thehydrocarbon material thus distilling off volatile constituents from thehydrocarbon material.

8. The method of a coal distillation plant having a plurality of ovensor retorts in which coal is being distilled, which comprises hot coalcarbonization gases from the plant to bubble through the dehydrated tarso as to heat distilling dehydrated tar at.

causing a portion of the fresh the tar and effect substantial cooling ofthe gases,

agitate it, and ter therefrom,

of volatile mat-

